This invention relates to polyamide formulations which are flame retardant and have improved melt flow.
Two of the most commercially significant polyamides are poly(hexamethyleneadipamide), M.sub.n 11,000 to 40,000, and polycaprolactam, M.sub.n 11,000 to 40,000. These two polyamides are commonly referred to as, respectively, nylon 6,6 and nylon 6, and will be so referred to herein.
Formulations containing nylon 6,6 or nylon 6 and a substantial load of fillers do not exhibit high melt flows under processing conditions even though these nylons are highly crystalline. (Fillers can include, inerts, flame retardants, pigments, thermal stabilizers, etc.) It is disadvantageous for a formulation to have a low melt flow as the molten formulation does not flow well or quickly in a mold which can result in burning and incomplete article formation.
In today's market there is significant need for nylon 6,6 and nylon 6 based formulations which are flame retardant. Excellent flame retardancy can be obtained by including in the formulation, as a flame retardant, a halogenated polyphenylene ether of the type disclosed in U.S. Pat. No. 3,760,003. In addition, flame retardant synergists, such as Sb.sub.2 O.sub.3 and Fe.sub.2 O.sub.3, are often used in cooperation with such halogenated polyphenylene ethers. While the flame retardancy of such formulations is very high, e.g. a UL-94 rating of V-0, these formulations have a very low melt flow, e.g. a melt index of 2.5 g/10 min. ASTM 1238 k. With this low of a melt flow, processing of these formulations is difficult at best and productivity may suffer as a result.
The melt flow of such nylon 6,6 or nylon 6/halogenated polyphenylene ether formulations can be significantly improved by the use of a plasticizer, such as o- or p-toluenesulfonamide. Such plasticizers are not necessarily a panacea though, as many increase the flammability of the formulation and contribute to a lowering of the heat deflection temperature of articles made from the plasticizer containing formulation.
It is therefore an object of this invention to provide formulations which include nylon 6,6, nylon 6 or a mixture thereof, halogenated polyphenylene ether and, optionally, a flame retardant synergist, which formulations have both improved melt flow and high flame retardancy.